Separating nonlinear optical effects in optical limiters

Overview

Optical limiting uses a medium’s nonlinear response to allow light at low intensities to be transmitted, but restricts transmission at high intensities so as to safeguard sensitive detectors including the eye. A popular nonlinear process used in optical limiters is two photon absorption where two high intensity light photons are simultaneously absorbed thereby reducing the light transmission through the medium. Unfortunately, in gold nanoparticle optical limiters a second nonlinear process can arise – saturated absorption which leads to an increase in light transmission at high intensities - reducing the effectiveness of the optical limiter. This project will explore the fundamental light material interaction processes underlying these two competing nonlinear processes to determine whether it is possible to suppress the undesired saturated absorption.

Research activities

In this project you will:

• be working within a team consisting of academic, post-doctoral and higher degree researchers.
• use QUT's wavelength tunable nanosecond laser system to measure light transmission through a range of gold nanoparticle mixtures.
• set up optical experiments to test your ideas and gather data.
• analyze the results through existing electromagnetic theories for modelling light absorption and nonlinear absorption.
• present and discuss your results at regular team meetings which will inform strategies for separating the competing nonlinear optical processes.
• prepare written reports of your results that will be incorporated into papers and other research outputs.

Outcomes

1. The project aims to better understand the physical processes that underpin two photon absorption and saturated absorption in gold nanoparticle media.
2. To use that understanding to determine the light and material properties necessary to separate two photon absorption from saturated absorption.
3. Apply that knowledge to design and develop superior optical limiters.

Skills and experience

This project involves a blend of theoretical and experimental activities with the proportion determined through your background and interests. Some experience in optics or physics in general is desirable but not essential. Data analysis and report writing will require familiarity with standard computing packages (eg. Word, excel, etc) and experience with MatLab would be helpful.

Scholarships

You may be eligible to apply for a research scholarship.

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Keywords

• Laser
• optic
• absorption
• nonlinear
• nanoparticle
• physics

Contact

Contact the supervisor for more information.